How can I get the board to accept my ideas over his?
It sounds as if winning this argument is important to you personally, not just for the company. When we feel strongly about something, at work or at home, it is not unusual to generate animosity towards those who represent what we construe as the opposite of our point of view. What might start off as logical and rational quickly becomes personal. It's important to us to 'win'.
This is a natural reaction but one that needs to be transcended. The more adversarial you become, the more closed your mind is to other possibilities, including the one that the other guy might be right. You also make it easier for the board to think you are pursuing your own agenda, rather than one that is genuinely for the benefit of the business. And, in these circumstances, if you succeed in getting your way by force, your victory will be a hollow one, because you will have set up an antipathy that gets in the way of the effective functioning of the company.
Research among successful leaders shows an ability to resolve dilemmas as a key distinguishing feature. In wanting the board to accept your ideas over your fellow director's, you are pushing for a resolution that is less than optimal. As my colleague Ginger Chih says: 'The strongest position is in the integration of opposites. In trying to force acceptance of your view, you are asking the board to take on the weakness of both cases, not their strength.'
Your ideas could lead to success; his ideas could be damaging: both assertions bear some investigation. Unfortunately, in trying to resolve the issues, the result is often lowest-common-denominator thinking, rather than highest common multiple, agreeing a compromise rather than finding a solution that incorporates the best understanding and ideas all parties can bring.
Any strategy is only as strong as its weakest assumption in the argument, so it's worth working out what are the less robust points of your logic chain. Identifying these will enable you to improve your strategy, seek data that will validate your hypotheses, and perhaps even question and change some aspects of your plan. Going through the discipline of trying to see things from an opposite perspective will be helpful and will encourage you to structure your case in terms that address likely objections.
Jung identified two polar opposites in the way people see the world: those who are keenly aware of the here and now, who base their views on hard facts and solve problems by reference to past experience; and those who see the big picture, are future-focused, who come up with an overall solution and work back to the details of how it will be implemented. I suspect you are inclined to the latter approach, while your sales director is closer to the former. Both ends of the spectrum have value in problem-solving, and if you can incorporate some of the other sort of thinking in your strategy, both you and your company will benefit.
One approach would be to ask sales people to feed back any trends they pick up in their travels. After all, sales forces are the people who have the most frequent contact with customers and so are the best placed to know what's going on here and now.
This is not to deny the importance of the wider perspective that marketing can bring. If the organisation doesn't keep an eye out for what's over the hill, for what will affect the future fortunes of the company (legislation, technology, social change etc), there's a danger that the main business opportunity will move elsewhere and the company will be stranded. In 1992 Microsoft had only three internet access points in the entire organisation; the company thought this would reduce the security risk and, anyway, had no immediate evidence that the internet was going to be an important channel.
Bill Gates, however, took stock of what he was hearing in terms of the current reality as well as the future and decided to reverse company policy, a decision that has had a major impact on the company's success.
The more senior we become in our roles, the greater the need to get to grips with dilemmas. You may cherish thoughts of becoming a managing director in time. If that happens you'll need to be able to take a balanced view, to draw the best from all the resources of the company. Starting to adopt this kind of thinking now will be good practice for that next level.